The present invention resides in novel methods and apparatus for stressing muscles of the human body in the region of the lower trunk including the spine and abdomen, for purposes of testing the strength of, or exercising, these muscles. More specifically, the muscles concerned herein are those which move the spine rearward, i.e., the lumbar or spinal erector muscles; those which move the spine forwardly, i.e., the abdominal muscles; and those muscles which rotate or twist the spine about the spinal axis, i.e., the rotary torso muscles. As used herein, the term "lower trunk" includes the region of the human body above the pelvis and which includes the aforementioned muscles and which, of course, excludes the head, neck and limbs of the body. The lumbar, abdominal and rotary torso muscles are connected to the lower spine which is founded on the pelvis. The lumbar muscles are connected to and support the lower spine at the five lowermost vertabrae.
It is now fairly well-established that most injuries to the lower back in the region of the lumbar are due to failure of the lumbar muscles rather than the spine itself. Thus, it is not unusual in back injury cases, to find the spine in order but with pain or malfunction still persisting in the lower back. In such cases, it is obvious that treatment to the spine itself will not alleviate or cure the problem.
It is my belief that attempts by others thus far to test and/or exercise the lumbar muscles have failed due to the inability to immobilize the gluteus maximus and hamstring muscles during such tests or exercise. The latter muscles are connected to the femurs of the thighs which femurs are mounted in sockets in the pelvis. Unless the gluteus and hamstring muscles are immobilized during tests of the lumbar muscles, the former muscles will become involved to render the tests as inaccurate and misleading. Similarly, any intended exercise of the lumbar muscles while the gluteus and hamstrings are free to assist the lumbar muscles, will be inefficient if not ineffective.
In addition to being inaccurate in the manner described above, prior methods and apparatus have been further inaccurate because they fail to take into account the position of the patient during a test. In other words, they fail to correlate the strength of the muscles tested with the position of the patient during the test. It is proven fact that the strength of muscles will vary with the position of the patient or the muscles during the test. Indeed, it has been proven that slight variations in position can produce substantial differences in muscle strength. It therefore follows that to achieve accurate test results and to properly compare them with past or future results, the muscles must be tested while the patient is in a predetermined or known position.
In addition to being ineffective or inefficient, some "dynamic" methods of the prior art for exercising the lower back are believed to be unsatisfactory from the standpoint of safety. This is due to impact loads imparted to the body during such exercise, for example, when relatively high kinetic energy is generated in a mass being repetitively lifted and released by the exerciser.